Re-Design and Optimization of Critical Mechanical Components of Oil Filled Power Transformers

Abstract

A transformer is a vital component in any industry. If the transformer fails, the electric supply fails. So it is very necessary that the transformer must work without any interruption. Transformer has many components and all are essential for its smooth working. So every component in transformer is critical. This dissertation mainly focuses on four critical parts of oil filled transformer. The first one is conservator. It acts as an oil reservoir, which allows expansion and contraction of transformer oil to prevent the damage to the tank. So, the problem to optimize the weight and also to reduce the variety of the sizes available with the industry has been taken for dissertation. The second issue for the dissertation work focuses on the development of particular methodology for preparation of core of the transformer. Very high force is required to tighten the pressure bolts after the core is prepared which is not possible to apply manually. Hence some core clamping arrangement is to be developed, which reduces the human effort. The third problem is about the core frame. It is said that the core and winding are called the heart of a transformer. The core frame is mounted on top and bottom of the core and winding assembly. Core frame is made up of mild steel. In transformer, there are several losses occur which decrease the efficiency of transformer. ‘Stray loss’ is one on the major loss which effe cts badly on performance of transformer. This stray loss occurs due to the presence of mild steel in transformer. So if the weight of the core frame is reduced by optimization, it will have large impact on the reduction of stray losses and improvement of transformer efficiency. Thus, the problem of the optimization of core frame to reduce the weight of mild steel used has been taken. The application of the transformer covers large spectrum of industries. Hence the location of the erection of transformer assemblies varies from sea level to the very high on the mountain. Almost all regions experience the earthquake with varying severity. This seismic activity will affect the functionality of a transformer. It may fail under action of earthquake. So, step by step procedure for calculating required foundation bolt size under the effect of seismic and wind loading should be developed. Hence last problem is about the developing methodology to determine the foundation bolt size for transformer. The present report describes the solution of above said issues. The conservator problem has been solved and the design for the same has been optimized for reduction in weight using classical optimization technique called Lagrange Multiplier. The second issue regarding the clamping arrangement problem for the core has been solved by developing large capacity C clamp arrangement. For the solution towards the third problem, one particular model of transformer assembly has been taken and using CAE tools, the size of the core frame structure haWWs been reduced by the size optimization using HyperMesh. For the performance of transformer assembly under the event of earthquake, the required foundation bolt size has been evaluated for particular model of the transformer using static equivalent method.